Semiconductor device and method of manufacturing the same

ABSTRACT

To a provide a method of forming a layered film of a silicon nitride film and a silicon oxide film on a glass substrate in a short time without requiring a plurality of film deposition chambers. In a thin film transistor, a layered film including a silicon nitride oxide film ( 12 ) is formed between a semiconductor layer ( 13 ) and a substrate ( 11 ) using the same chamber. The silicon nitride oxide film has a continuously changing composition ration of nitrogen or oxygen. An electric characteristic of the TFT is thus improved.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a semiconductor device having acircuit constructed of a thin film transistor (hereinafter referred toas TFT) and a method of manufacturing the same. For example, the presentinvention relates to an electro-optical device typified by a liquidcrystal display panel and to electronic equipment having such anelectro-optical device mounted thereon as its component.

[0003] It is to be noted that a semiconductor device as stated hereinthroughout the present specification denotes a general device whichfunctions by utilizing semiconductor characteristics, and thatelectro-optical devices, semiconductor circuits, and electronicequipments are all semiconductor devices.

[0004] 2. Description of the Related Art

[0005] A technique for structuring a thin film transistor (TFT) using asemiconductor thin film (having a thickness on the order of aboutseveral to several hundred nm) formed on a substrate having aninsulating surface has been attracting much attention in recent years.Thin film transistors are widely applied to electronic devices such asan IC or an electro-optical device, and in particular, development ofthe TFT as a switching element of an image display device is proceedingrapidly.

[0006] Typically, an amorphous silicon film, a crystalline silicon filmformed from an amorphous silicon film that is crystallized by a knownmethod such as laser light annelaing, or like other film is used as amaterial of the semiconductor thin film. In particular, the TFT usingthe crystalline silicon film as an active layer realizes a high electricfield mobility, and hence its ability in current driving is high, makingit possible to perform fine processing and increasing an aperture ratioof a pixel portion.

[0007] An active matrix liquid crystal display device that utilizes suchTFTs as switching elements of pixels and as driver circuits isattracting much attention. Utilizing an inexpensive glass substraterather than an expensive quartz substrate becomes the premise to realizean inexpensive as well as a large screen display device. Furthermore, itis demanded that the highest temperature in a manufacturing process beset at 600 to 700° C. or lower when taking the heat resistancetemperature of the glass substrate in consideration.

[0008] However, a large quantity of impurity ions of alkali metal suchas sodium (Na), or other impurities are contained in the glasssubstrate. A base film (blocking layer) formed from a silicon oxidefilm, a silicon nitride film, or the like is therefore formed on thesurface of the glass substrate on which the TFTs will be formed in orderto prevent the impurity ions of the alkali metal element, etc. frompenetrating into the active layer of the TFT.

[0009] An electric field is formed in the active layer when a voltage isapplied to a gate electrode of the TFT, whereby the impurity ions in theglass substrate are drawn to the active layer. As a result, if theimpurity ions pass through the base film and penetrate into a gateinsulating film and the active layer, then an electrical characteristicwill undergo a fluctuation, thereby leading to the reduction inreliability.

[0010] In the case of a top gate TFT, in particular, the film quality ofthe base film influences the characteristic of the TFT immensely becausea channel forming region is in contact with the base film.

[0011] Conventionally, the silicon nitride (SiN_(x)) film and thesilicon oxide (SiO_(x)) film are generally used as the base film.Although it is known that an insulating film formed from the siliconnitride (SiN_(x)) film is high in its blocking effect of impurity ions,the insulating film has a great number of trap levels and therefore hasa huge influence on the characteristic of the TFT. In addition, thesilicon oxide film has merits such as a wider band gap, a higherinsulation, and a lower trap level compared with the silicon nitridefilm. The silicon oxide film, however, has demerits in that it is apt toabsorb moisture and also has a low blocking effect of impurity ions.

[0012] Besides, in the case of using a layered film of the siliconnitride (SiN_(x)) film and the silicon oxide (SiO_(x)) film as the basefilm, it is also known that the layered film has an effect onimprovement in stability of the TFT characteristic.

[0013] When forming the layered film formed of the silicon nitride filmand the silicon oxide film on the glass substrate, two film depositionchambers were necessary to exclusively form these films individuallybecause the composition elements of the silicon nitride film and thesilicon oxide film are respectively different.

[0014] Furthermore, in the case of using two film deposition chambers toform the layered film, a conveying time when conveying the substrate anda heating time for heating the substrate which has grown cold whilebeing conveyed are required, thereby inviting an increase in theprocessing time.

SUMMARY OF THE INVENTION

[0015] The present invention has been made to solve the above problem,and therefore has an object to provide a base film formation methodhaving excellent productivity and a base film attained through thisformation method.

[0016] According to a first aspect of the present invention, there isprovided a semiconductor device having a thin film transistor,characterized in that the semiconductor device comprises an insulatingfilm in contact with a substrate and a semiconductor film on theinsulating film and in contact thereto, and that the insulating film isa silicon nitride oxide film in which a concentration ratio of nitrogento a concentration of silicon in the film undergoes a continuous changewithin a range of 0.3 or more and 1.6 or less. Therefore, from TFTcharacteristics so far, remarkable progress can be made in an electriccharacteristic of a TFT using the semiconductor film that is in contactwith the silicon nitride oxide film as an active layer.

[0017] According to a second aspect of the present invention, there isprovided a semiconductor device having a thin film transistor,characterized in that the semiconductor device comprises a layered filmincluding an insulating film in contact with a substrate and asemiconductor film on the insulating film and in contact thereto, andthat the insulating film is a silicon nitride oxide film in which aconcentration ratio of oxygen to a concentration of silicon in the filmundergoes a continuous change within a range of 0.1 or more and 1.7 orless. Therefore, from TFT characteristics so far, remarkable progresscan be made in an electric characteristic of a TFT using thesemiconductor film that is in contact with the silicon nitride oxidefilm as an active layer.

[0018] According to a third aspect of the present invention, there isprovided a semiconductor device having a thin film transistor,characterized in that the semiconductor device comprises an insulatingfilm in contact with a substrate and a semiconductor film on theinsulating film and in contact thereto; and that the insulating film isa silicon nitride oxide film in which a concentration ratio of nitrogento a concentration of silicon in the film undergoes a continuous changewithin a range of 0.3 or more and 1.6 or less and a concentration ratioof oxygen to a concentration of silicon in the film undergoes acontinuous change within a range of 0.1 or more and 1.7 or less.Therefore, from TFT characteristics so far, remarkable progress can bemade in an electric characteristic of a TFT using the semiconductor filmthat is in contact with the silicon nitride oxide film as an activelayer.

[0019] According to a fourth aspect of the present invention, there isprovided a semiconductor device having a thin film transistor,characterized in that the semiconductor device comprises a layered filmincluding a silicon nitride oxide film in contact with a substrate and asemiconductor film on the layered film and in contact thereto, and thatthe layered film including the silicon nitride oxide film includes onelayer of film in which a concentration ratio of nitrogen to aconcentration of silicon in the film undergoes a continuous changewithin a range of 0.3 or more and 1.6 or less. Therefore, from TFTcharacteristics so far, remarkable progress can be made in an electriccharacteristic of a TFT using the semiconductor film that is formed on abase film containing the silicon nitride oxide film as an active layer.

[0020] According to a fifth aspect of the present invention, there isprovided a semiconductor device having a thin film transistor,characterized in that the semiconductor device comprises a layered filmincluding a silicon nitride oxide film in contact with a substrate and asemiconductor film on the layered film and in contact thereto, and thatthe layered film including the silicon nitride oxide film includes onelayer of film in which a concentration ratio of oxygen to aconcentration of silicon in the film undergoes a continuous changewithin a range of 0.1 or more and 1.7 or less. Therefore, from TFTcharacteristics so far, remarkable progress can be made in an electriccharacteristic of a TFT using the semiconductor film that is formed on abase film containing the silicon nitride oxide film as an active layer.

[0021] According to a sixth aspect of the present invention, there isprovided a semiconductor device having a thin film transistor,characterized in that the semiconductor device comprises a siliconnitride oxide film in contact with a substrate, a silicon oxide film onthe silicon nitride oxide film and in contact thereto, and asemiconductor film on the silicon oxide film and in contact thereto, andthat the silicon nitride oxide film is a film in which a concentrationratio of nitrogen to a concentration of silicon in the film undergoes acontinuous change within a range of 0.3 or more and 1.6 or less.Therefore, from TFT characteristics so far, remarkable progress can bemade in an electric characteristic of a TFT using the semiconductor filmthat is formed on a base film containing the silicon nitride oxide filmas an active layer.

[0022] According to a seventh aspect of the present invention, there isprovided a semiconductor device having a thin film transistor,characterized in that the semiconductor device comprises a siliconnitride oxide film in contact with a substrate, a silicon oxide film onthe silicon nitride oxide film and in contact thereto, and asemiconductor film on the silicon oxide film and in contact thereto; andthat the silicon nitride oxide film is a film in which a concentrationratio of oxygen to a concentration of silicon in the film undergoes acontinuous change within a range of 0.1 or more and 1.7 or less.Therefore, from TFT characteristics so far, remarkable progress can bemade in an electric characteristic of a TFT using the semiconductor filmthat is formed on a base film containing the silicon nitride oxide filmas an active layer.

[0023] According to an eighth aspect of the present invention, thesemiconductor device as set forth in any one of the first to seventhaspects of the present invention is characterized in that the nitrogenconcentration in the silicon nitride oxide film continuously decreasestoward an interface of the semiconductor film side.

[0024] According to a ninth aspect of the present invention, thesemiconductor device as set forth in any one of the first to eighthaspects of the present invention is characterized in that the oxygenconcentration in the silicon nitride oxide film continuously increasestoward an interface of the semiconductor film side.

[0025] Further, according to a tenth aspect of the present invention, inorder to realize any one of the first to ninth aspects of the presentinvention, there is provided a method of manufacturing a semiconductordevice, characterized by comprising a step of forming a silicon nitrideoxide film in which a concentration ratio of nitrogen to a concentrationof silicon in the film undergoes a continuous change within a range of0.3 or more and 1.6 or less by continuously altering a gas flow ratewithin a fixed period.

[0026] Further, according to an eleventh aspect of the presentinvention, there is provided a method of manufacturing a semiconductordevice, characterized by comprising a step of forming a silicon nitrideoxide film in which a concentration ratio of oxygen to a concentrationof silicon in the film undergoes a continuous change within a range of0.1 or more and 1.7 or less by continuously altering a gas flow ratewithin a fixed period.

[0027] Further, according to a twelfth aspect of the present invention,there is provided a method of manufacturing a semiconductor device,characterized by comprising a step of forming a silicon nitride oxidefilm in which a concentration ratio of nitrogen to a concentration ofsilicon in the film undergoes a continuous change within a range of 0.3or more and 1.6 or less by continuously altering a gas ratio within afixed period.

[0028] Further, according to a thirteenth aspect of the presentinvention, there is provided a method of manufacturing a semiconductordevice, characterized by comprising a step of forming a silicon nitrideoxide film in which a concentration ratio of oxygen to a concentrationof silicon in the film undergoes a continuous change within a range of0.1 or more and 1.7 or less by continuously altering a gas ratio withina fixed period.

[0029] Further, according to a fourteenth aspect of the presentinvention, there is provided a method of manufacturing a semiconductordevice, characterized by comprising a step of forming a silicon nitrideoxide film in which a concentration ratio of nitrogen to a concentrationof silicon in the film undergoes a continuous change within a range of0.3 or more and 1.6 or less by continuously altering an RF output withina fixed period.

[0030] Further, according to a fifteenth aspect of the presentinvention, there is provided a method of manufacturing a semiconductordevice, characterized by comprising a step of forming a silicon nitrideoxide film in which a concentration ratio of oxygen to a concentrationof silicon in the film undergoes a continuous change within a range of0.1 or more and 1.7 or less by continuously altering an RF output withina fixed period.

[0031] Further, according to a sixteenth aspect of the presentinvention, there is provided a method of manufacturing a semiconductordevice, characterized by comprising a step of forming a silicon nitrideoxide film in which a concentration ratio of nitrogen to a concentrationof silicon in the film undergoes a continuous change within a range of0.3 or more and 1.6 or less and a semiconductor film consecutively inthe same film deposition chamber.

[0032] Further, according to a seventeenth aspect of the presentinvention, there is provided a method of manufacturing a semiconductordevice, characterized by comprising a step of forming a silicon nitrideoxide film in which a concentration ratio of oxygen to a concentrationof silicon in the film undergoes a continuous change within a range of0.1 or more and 1.7 or less and a semiconductor film consecutively inthe same film deposition chamber.

[0033] Further, according to an eighteenth aspect of the presentinvention, there is provided a method of manufacturing a semiconductordevice, characterized by comprising a step of forming an insulatingfilm, a silicon nitride oxide film in which a concentration ratio ofnitrogen to a concentration of silicon in the film undergoes acontinuous change within a range of 0.3 or more and 1.6 or less, and asemiconductor film consecutively in the same film deposition chamber.

[0034] Further, according to a nineteenth aspect of the presentinvention, there is provided a method of manufacturing a semiconductordevice, characterized by comprising a step of forming an insulatingfilm, a silicon nitride oxide film in which a concentration ratio ofoxygen to a concentration of silicon in the film undergoes a continuouschange within a range of 0.1 or more and 1.7 or less, and asemiconductor film consecutively in the same film deposition chamber.

[0035] Further, according to a twentieth aspect of the presentinvention, there is provided a method of manufacturing a semiconductordevice, characterized by comprising a step of forming a silicon nitrideoxide film in which a concentration ratio of nitrogen to a concentrationof silicon in the film undergoes a continuous change within a range of0.3 or more and 1.6 or less, an insulating film, and a semiconductorfilm consecutively in the same film deposition chamber.

[0036] Further, according to a twenty-first aspect of the presentinvention, there is provided a method of manufacturing a semiconductordevice, characterized by comprising a step of forming a silicon nitrideoxide film in which a concentration ratio of oxygen to a concentrationof silicon in the film undergoes a continuous change within a range of0.1 or more and 1.7 or less, an insulating film, and a semiconductorfilm consecutively in the same film deposition chamber.

[0037] Further, according to a twenty-second aspect of the presentinvention, there is provided a method of manufacturing a semiconductordevice, characterized by comprising a step of forming a first insulatingfilm, a silicon nitride oxide film in which a concentration ratio ofnitrogen to a concentration of silicon in the film undergoes acontinuous change within a range of 0.3 or more and 1.6 or less, and asecond insulating film consecutively in the same film depositionchamber.

[0038] Further, according to a twenty-third aspect of the presentinvention, there is provided a method of manufacturing a semiconductordevice, characterized by comprising a step of forming a first insulatingfilm, a silicon nitride oxide film in which a concentration ratio ofoxygen to a concentration of Si in the film undergoes a continuouschange within a range of 0.1 or more and 1.7 or less, a secondinsulating film, and a semiconductor film consecutively in the same filmdeposition chamber.

[0039] Further, according to a twenty-fourth aspect of the presentinvention, the method of manufacturing a semiconductor device as setforth in any one of the tenth to twenty-third aspects of the presentinvention is characterized in that the nitrogen concentration in thesilicon nitride oxide film is continuously decreased toward an interfaceof the semiconductor film side.

[0040] Still further, according to a twenty-fifth aspect of the presentinvention, the method of manufacturing a semiconductor device as setforth in any one of the tenth to twenty-fourth aspects of the presentinvention is characterized in that the oxygen concentration in thesilicon nitride oxide film is continuously increased toward an interfaceof the semiconductor film side.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In the accompanying drawings:

[0042]FIG. 1 is a diagram showing a manufacturing process in accordancewith Embodiment 1 of the present invention;

[0043]FIG. 2 is a diagram showing a manufacturing process in accordancewith Embodiment 2 of the present invention;

[0044]FIG. 3 is a diagram showing a manufacturing process in accordancewith Embodiment 3 of the present invention;

[0045]FIG. 4 is a diagram showing a manufacturing process in accordancewith Embodiment 4 of the present invention;

[0046]FIG. 5 is a diagram showing a manufacturing process in accordancewith Embodiment 5 of the present invention;

[0047]FIGS. 6A to 6C are diagrams showing manufacturing processes of anAM-LCD in accordance with Embodiment 6 of the present invention;

[0048]FIGS. 7A to 7C are diagrams showing the manufacturing processes ofthe AM-LCD in accordance with Embodiment 6 of the present invention;

[0049]FIG. 8 is a diagram showing the manufacturing process of theAM-LCD in accordance with Embodiment 6 of the present invention;

[0050]FIGS. 9A to 9B are diagrams showing the manufacturing processes ofthe AM-LCD in accordance with Embodiment 6 of the present invention;

[0051]FIG. 10 is a view showing a cross-sectional structure of theactive matrix liquid crystal display device in accordance withEmbodiment 6 of the present invention;

[0052]FIG. 11 is view showing an outer appearance of the AM-LCD ofEmbodiment 6 of the present invention;

[0053]FIG. 12 is a diagram showing a portion of a top view of a pixelportion in accordance with Embodiment 6 of the present invention;

[0054]FIGS. 13A and 13B are diagrams showing manufacturing processes ofan AM-LCD in accordance with Embodiment 7 of the present invention;

[0055]FIGS. 14A and 14B are diagrams showing the manufacturing processesof the AM-LCD in accordance with Embodiment 7 of the present invention;

[0056]FIGS. 15A and 15B are diagrams showing manufacturing processes ofan AM-LCD in accordance with Embodiment 8 of the present invention;

[0057]FIGS. 16A to 16F are views showing examples of electronicequipments of Embodiment 9 of the present invention;

[0058]FIGS. 17A to 16D are views showing examples of electronicequipments of Embodiment 9 of the present invention;

[0059]FIGS. 18A to 18C are views showing examples of electronicequipments of Embodiment 9 of the present invention; and

[0060]FIG. 19 is a view showing an example of a manufacturing device inaccordance with Embodiment 1 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0061] Hereinafter, an embodiment mode of the present invention will beexplained.

[0062] The present invention will provide a silicon nitride oxide filmin which either a concentration ratio of nitrogen to a concentration ofsilicon in the film or a concentration of oxygen to the concentration ofsilicon in the film under a continuous change and a method ofmanufacturing thereof.

[0063] To be more specific, the concentration ratio of nitrogen to theconcentration of silicon in the silicon nitride oxide film of thepresent invention undergoes a continuous change within a range of 0.3 ormore and 1.6 or less. It is to be noted that preferably the nitrogenconcentration in the silicon nitride oxide film formed in contact with asemiconductor film is continuously decreased toward an interface of thesemiconductor film side. If the nitrogen concentration is high in aninsulating film, then its insulating characteristic is reduced due to agreat number of fixed electric charges. Therefore, the semiconductorfilm is formed contacting the insulating film so that when a TFT usesthis semiconductor film as an active layer, it facilitates the formingof trap levels in the interface of the silicon nitride oxide film andthe active layer.

[0064] Furthermore, the concentration ratio of oxygen to theconcentration of silicon in the silicon nitride oxide film of thepresent invention undergoes a continuous change within a range of 0.1 ormore and 1.7 or less. It is to be noted that preferably the oxygenconcentration in the silicon nitride oxide film formed in contact withthe semiconductor film is continuously increased toward the interface ofthe semiconductor film side.

[0065] The concentration ratio of the silicon nitride oxide film formedby the present invention is continuously changed, and therefore thesilicon nitride oxide film has the same function as that of a layeredfilm formed of a silicon nitride film and a silicon oxide film. Inessence, because formation is conducted in the same reaction chamber, inaddition to being able to reduce unevenness caused by contamination orthe like during the conveying of a substrate, unevenness between lotsand between substrates can be reduced together with improvingproductivity when compared with the conventional way of forming thelayered film in individual reaction chambers.

[0066] The silicon nitride oxide film formed by the present inventionalso has effects in blocking impurities and improving the resistance ofthermal stress by alleviating the influences due to the contraction ofthe substrate.

[0067] In the layered film of the silicon nitride film and the siliconoxide film, there is a problem in which the film peels off due to astress developing in the interface between the films. However, thesilicon nitride oxide film formed by the present invention is a singlelayer, and thus there is no existence of an interface. Therefore,drawbacks such as the peeling off of a film due to stress developing inthe interface will not occur.

[0068] CVD methods such as plasma CVD, low pressure CVD, and ECR CVD maybe employed to form the silicon nitride oxide film of the presentinvention. Furthermore, the silicon nitride oxide film of the presentinvention is characterized in that it is formed in one film depositionchamber. In the silicon nitride oxide film, the composition ratio ofsilicon, oxygen, nitrogen, and hydrogen is controlled by regulating aflow rate of source gas, a temperature of the substrate, pressure, an RFpower, and an interval between electrodes. SiH₄, N₂O, and NH₃ are usedas the source gases. Furthermore, N₂ may be added to these source gases.Si₂H₆ (disilane) can be used as the silicon source instead of SiH₄(monosilane). NH₃ is for supplementing the effect of nitrogenating N₂O(nitrous oxide), and hence the nitrogen concentration of the siliconnitride oxide film can be made higher by doping NH₃. N₂O, which is alsothe oxygen source, can be used instead of NH₃. Moreover, either O₂ or O₃can be used as the oxygen source.

[0069] Note that in the case of forming the silicon nitride oxide filmby a CVD method, the composition not only contains silicon, oxygen, andnitrogen, but hydrogen which is contained in the source gas is alsoincluded in the composition.

[0070] A base film in contact with the substrate is formed into alaminate structure, and thus in the case of using the silicon nitrideoxide film of the present invention as at least one of the layers,relaxation of stress between the films themselves and improvement of theadherence between the films can be carried out.

[0071] For example, when the silicon nitride oxide film of the presentinvention is provided in contact with the semiconductor film as shown inFIG. 2, relaxation of stress and adherence between the insulating filmformed under the silicon nitride oxide film of the present invention andthe semiconductor film are improved.

[0072] Further, as shown in FIG. 3, in the case of providing the siliconnitride oxide film of the present invention in contact with thesubstrate, then the relaxation of stress and adherence between theinsulating film formed on the silicon nitride oxide film of the presentinvention and the substrate are improved.

[0073] Note that the silicon nitride oxide film of the present inventionand the insulating film can be freely combined as shown in FIGS. 4 and5.

[0074] A silicon oxide film or a silicon nitride film having silicon asits main constituent can be cited as the above-mentioned insulatingfilm. Further, CVD methods such as plasma CVD, low pressure CVD, and ECRCVD can be used in the film deposition method of these films. In thesource gases used in forming the silicon oxide film, an inorganic silanesuch as SiH₄ (monosilane) or Si₂H₆ (disilane) can be used as the siliconsource, and O₂, O₃, or N₂O can be used as the oxygen source.

[0075] A general silicon nitride oxide film can also be used as theabove-mentioned insulating film. It is to be noted that in the generalsilicon nitride oxide film, the nitrogen concentration or the oxygenconcentration in the film is roughly uniform in the direction of thefilm thickness, and hence does not have composition gradient. It istherefore a film that is entirely different from the silicon nitrideoxide film of the present invention.

[0076] For example, as shown in FIG. 3, the general silicon nitrideoxide film may be used as the insulating film to thereby form on thesubstrate a laminate layer of the silicon nitride oxide film of thepresent invention and the general silicon nitride oxide film.

[0077] Further, as shown in FIG. 4, the general silicon nitride oxidefilm may be used as a first insulating film and a second insulating filmto thereby form a laminate layer on the substrate in the order of thefirst silicon nitride oxide film, the silicon nitride oxide film of thepresent invention, and the second silicon nitride oxide film. Also, itgoes without saying that the silicon nitride oxide films can be freelycombined as shown in FIG. 5.

[0078] The semiconductor film is formed in contact with the base filmmade from the above-described silicon nitride oxide film of the presentinvention or in contact with the base film formed from a laminatestructure containing at least one layer of the silicon nitride oxidefilm of the present invention.

[0079] In the present invention, the semiconductor film is a non-singlecrystal semiconductor film, an amorphous semiconductor film, anamorphous semiconductor film having micro crystals, and a crystallinesemiconductor film. The crystalline semiconductor film is asemiconductor film that has crystallinity, for example, amicrocrystalline semiconductor film and a polycrystalline semiconductorfilm. Further, silicon, germanium, silicon germanium, a compoundsemiconductor film, etc. can be used as the semiconductor film. In thecase of the amorphous semiconductor film, the semiconductor film havingmicro crystals, and the microcrystalline semiconductor film are formed,it is preferable that the crystallinity of these films are improvedthrough heat treatment and laser irradiation to thereby be used as theactive layer of the TFT.

[0080] Further, in order to prevent contamination of the substrateduring conveyance, forming the above semiconductor film in successionwith the base film is preferred. Contamination to the interface of theinsulating film and the active layer can be prevented by forming thefilms in succession, resulting in facilitating the control of thecharacteristics of the TFT. In addition, by forming the abovesemiconductor film and the base film in succession, the process time isshortened, thereby improving productivity.

[0081] Therefore, from TFT characteristics so far, it is possible tomake remarkable progress in the electric characteristic of the TFT usingthe semiconductor film that is formed on the base film containing theabove-mentioned silicon nitride oxide film of the present invention asan active layer Hereinafter, embodiments of the present invention willbe explained in more detail in regards to the present invention adoptingthe above structure.

[0082] [Embodiment 1]

[0083] An explanation on a process of manufacturing a silicon nitrideoxide film that utilizes the present invention and a semiconductor film(crystalline silicon film in Embodiment 1) will be made. Embodiment 1 isshown in the following with reference to FIG. 1.

[0084] First of all, a silicon nitride oxide film 12 in which aconcentration ratio of nitrogen to a concentration of silicon in thefilm or a ratio concentration of oxygen to a concentration of silicon inthe film undergoing a continuous change is formed on a substrate 11.

[0085] A sheet-fed style plasma CVD apparatus (composed of a substrateconveying chamber 1011, load lock chambers 1012 and 1013, a first filmdeposition chamber 1014, a second film deposition chamber 1015, gatevalves 1016 to 1019, etc.) shown in FIG. 19 is utilized in Embodiment 1.

[0086] The substrate 11 is first set on a cassette 1021 of the load lockchamber 1023.

[0087] Next, the substrate 11 is conveyed to the first film depositionchamber 1014 to thereby heat the substrate so that the substratetemperature is approximately 320° C. The substrate 11 may be firstheated by using a pre-heating chamber or the like before it is conveyedto the first film deposition chamber 1014.

[0088] A silicon nitride oxide film is next formed to a film thicknessof 50 nm on the substrate. Conditions of the first film deposition areset as follows: an introducing amount of SiH₄ gas is set to about 80sccm; an introducing amount of N₂O gas is set to about 200 sccm; anintroducing amount of NH₃ gas is set to about 720 sccm, a pressureinside the chamber is set to about 1.0 Torr, and an RF power that is tobe inputted is set to about 1500 W. Subsequently, the conditions arecontinuously altered within a predetermined period so that they arechanged from the conditions of the first film deposition to theconditions of the second film deposition.

[0089] Note that the conditions of the second film deposition are set asfollows: the substrate temperature is set to 320° C., the introducingamount of SiH₄ gas is set to about 30 sccm; the introducing amount ofN₂O gas is set to about 3000 sccm, the pressure inside the chamber isset to about 1.0 Torr, and the RF power that is to be inputted is set toabout 500 W.

[0090] The silicon nitride oxide film 12 in which the concentrationratio of nitrogen to the concentration of silicon in the film or theconcentration ratio of oxygen to the concentration of silicon in thefilm undergoing a continuous change is thus obtained. The siliconnitride oxide film 12 has a composition gradient within its film, andtherefore the nitrogen increases continuously toward an interface of thesubstrate side.

[0091] The substrate is next conveyed to the second film depositionchamber 1015 through the substrate conveying chamber after the gas inthe first film deposition chamber 1014 is vacuum drawn or replaced withan inert gas such as N₂.

[0092] Thereafter, a semiconductor film 13, which is an amorphoussilicon film here formed in the second film deposition chamber 1015, isformed in contact with the silicon nitride oxide film 12.

[0093] In Embodiment 1, because it is possible to form the siliconnitride oxide film 12 and the semiconductor film with the same filmdeposition method, both films may be formed in succession in the samechamber. Due to the fact that successive film deposition is performed,contamination may be prevented for a time during conveying of thesubstrate after the formation of the silicon nitride oxide film 12. As aresult, characteristic irregularities of the manufactured TFTs can bereduced.

[0094] The substrate with the amorphous silicon film formed thereon isthen conveyed to the load lock chamber 1012 through the substrateconveying chamber 1011 and set on a cassette 1022.

[0095] Next, a known crystallization technique is carried out to therebyform a crystalline semiconductor film on the substrate with the laminatelayer of the silicon nitride oxide film 12 and the amorphoussemiconductor film formed thereon.

[0096] Known techniques may be used for the remaining processes to formthe TFT.

[0097] [Embodiment 2]

[0098] An explanation on a process of manufacturing the silicon nitrideoxide film that utilizes the present invention and the semiconductorfilm (crystalline silicon film in Embodiment 2) will be made. Embodiment2 is shown in the following with reference to FIG. 2.

[0099] First, after the formation of a first insulating film 22 on asubstrate 21, the silicon nitride oxide film 12 (second insulating film)in which the concentration ratio of nitrogen to the concentration ofsilicon in the film or the concentration ratio of oxygen to theconcentration of silicon in the film undergoes a continuous change isformed thereon.

[0100] The first insulating film 22 (a generic term as used hereinthroughout the present specification indicating a silicon oxide film, asilicon nitride film, or a silicon nitride oxide film) is formed on thesubstrate 21 and in contact thereto to a film thickness of between 10and 400 nm by plasma CVD or sputtering.

[0101] Further, heat treatment may be performed after forming the firstinsulating film 22.

[0102] Next, similar to Embodiment 1, the conditions are continuouslyaltered within a predetermined period so that they are changed from theconditions of the first film deposition to the conditions of the secondfilm deposition thereby forming a silicon nitride oxide film 23.

[0103] In Embodiment 2, because it is possible to form the firstinsulating film 22 and the silicon nitride oxide film 23 with the samefilm deposition method, both films may be formed in succession in thesame chamber.

[0104] Similar to Embodiment 1, a semiconductor film 24, which is formedfrom an amorphous silicon film here, is formed next in contact with thesilicon nitride oxide film 23.

[0105] Furthermore, because it is possible to form the silicon nitrideoxide film 23 and the semiconductor film with the same film depositionmethod here, both films may be formed in succession in the same chamber.After the formation of the silicon nitride oxide film 23, it becomespossible to prevent contamination or the like of the surface by notexposing the substrate to the open atmosphere for a time during theconveying of the substrate. As a result, characteristic irregularitiesof the manufactured TFTs can be reduced.

[0106] Thereafter, a known crystallization technique is carried out tothereby form a crystalline semiconductor film on the substrate with thelaminate layer of the silicon nitride oxide film 23 and the amorphoussemiconductor film formed thereon.

[0107] Known techniques may be used for the remaining processes to formthe TFT. [Embodiment 3]

[0108] An explanation on a process of manufacturing the silicon nitrideoxide film that utilizes the present invention and the semiconductorfilm (crystalline silicon film in Embodiment 3) will be made. Embodiment3 is shown in the following with reference to FIG. 3.

[0109] First, after the formation of a silicon nitride oxide film 32(first insulating film) in which the concentration ratio of nitrogen tothe concentration of silicon in the film or the concentration ratio ofoxygen to the concentration of silicon in the film undergoes acontinuous change is formed on a substrate 31, a second insulating film33 is formed thereon, and then a semiconductor film 34 is further formedthereon.

[0110] Similar to Embodiment 1, the conditions are continuously alteredwithin a predetermined period so that they are changed from theconditions of the first film deposition to the conditions of the secondfilm deposition to thereby form a silicon nitride oxide film 32 incontact with the substrate.

[0111] Next, a silicon oxide film serving as the second insulating film33 is formed on the silicon nitride oxide film 32. The second insulatingfilm 33 (a generic term as used herein throughout the presentspecification indicating a silicon oxide film, a silicon nitride film,or a silicon nitride oxide film) is formed to a film thickness ofbetween 100 and 400 nm by plasma CVD or sputtering.

[0112] Further, heat treatment may be performed after forming the secondinsulating film 33.

[0113] In Embodiment 3, because it is possible to form the secondinsulating film 33 and the silicon nitride oxide film 32 with the samefilm deposition method, both films may be formed in succession in thesame chamber.

[0114] The semiconductor film, which is formed from an amorphous siliconfilm here, is formed next in contact with the silicon oxide film.

[0115] Furthermore, because it is possible to form the silicon nitrideoxide film 32 and the semiconductor film 34 with the same filmdeposition method here, both films may be formed in succession in thesame chamber. After the formation of the silicon nitride oxide film 32,it becomes possible to prevent contamination or the like of the surfaceby not exposing the substrate to the open atmosphere for a time duringthe conveying of the substrate. As a result, characteristicirregularities of the manufactured TFTs can be reduced.

[0116] Thereafter, a known crystallization technique is performed tothereby form a crystalline semiconductor film on the substrate with thelaminate layer of the silicon nitride oxide film 32, the secondinsulating film 33, and the amorphous semiconductor film formed thereon.

[0117] Known techniques may be used for the remaining processes to formthe TFT.

[0118] [Embodiment 4]

[0119] An explanation on a process of manufacturing the silicon nitrideoxide film and the semiconductor film (crystalline silicon film inEmbodiment 4) utilizing the present invention will be made. Embodiment 4is shown in the following with reference to FIG. 4.

[0120] First of all, a first insulating film 42 is formed from, here, asilicon nitride oxide film to a thickness of 50 nm on a substrate 41under the first conditions of the film deposition.

[0121] The first conditions of the film deposition are set as follows:substrate temperature is set to 320° C., the introducing amount of SiH₄gas is set to about 80 sccm; the introducing amount of N₂O gas is set toabout 200 sccm; the introducing amount of NH₃ gas is set to about 720sccm, the pressure inside the chamber is set to about 1.0 Torr, and theRF power that is to be inputted is set to about 1500 W.

[0122] Next, without setting the RF power to zero, the values of thepressure, the gas flow rate, and the RF output are continuously altereduntil they reach the values indicated by the second conditions of thefilm deposition, thereby forming a silicon nitride oxide film 43. Thesilicon nitride oxide film 43 is a film in which the concentration ratioof nitrogen to the concentration of silicon in the film or theconcentration ratio of oxygen to the concentration of silicon in thefilm is undergoing a continuous change. Though the time for thecontinuous change to take place may be appropriately determined, it isset to 10 seconds in Embodiment 4.

[0123] The second conditions of the film deposition are set as follows:the substrate temperature is set to 320° C., the introducing amount ofSiH₄ gas is set to about 30 sccm; the introducing amount of N₂O gas isset to about 3000 sccm, the pressure inside the chamber is set to about1.0 Torr, and the RF power that is to be inputted is set to about 500 W.

[0124] A second insulating film 44 is next formed under the secondconditions of the film deposition without setting the RF power to zero.The second insulating film 44 here is the silicon nitride oxide filmformed to a thickness of 100 nm.

[0125] Next, a semiconductor film 45 that is an amorphous silicon filmhere is formed on the second insulating film 44 and in contact thereto.

[0126] Further, because here it is possible to form the secondinsulating film 44 and the semiconductor film 45 with the same filmdeposition method, both films may be formed in succession in the samechamber. After the formation of the second insulating film 44, itbecomes possible to prevent contamination of the surface by not exposingthe substrate to the open atmosphere for a time during the conveying ofthe substrate. As a result, characteristic irregularities of themanufactured TFTs can be reduced.

[0127] Thereafter, a known crystallization technique is performed tothereby form a crystalline semiconductor film on the substrate with thelaminate layer of the first insulating film 42, the silicon nitrideoxide film 32, the second insulating film 44, and the amorphoussemiconductor film formed thereon.

[0128] Known techniques may be used for the remaining processes to formthe TFT.

[0129] [Embodiment 5]

[0130] An explanation on a process of manufacturing the silicon nitrideoxide film and the semiconductor film (crystalline silicon film inEmbodiment 5) utilizing the present invention will be made. Embodiment 5is shown in the following with reference to FIG. 5.

[0131] First of all, a first insulating film 52, a silicon nitride oxidefilm 53, and a second insulating film 54 are formed on a substrate 51 inaccordance with the processes of Embodiment 4. Since the processes untilthe formation of these films are the same as that of Embodiment 4,explanations thereof will be omitted here.

[0132] After obtaining the second insulating film 54, heat treatment isperformed on the substrate under a nitrogen atmosphere at 640° C. for 4hours by employment of an electric furnace. Heat stability can besecured through this heat treatment.

[0133] Subsequently, a silicon oxide film 55 is formed to a filmthickness of 20 nm by plasma CVD with TEOS as the source material. It isto be noted that the silicon nitride oxide film may be formed instead ofthe silicon oxide film.

[0134] Next, a semiconductor film 56 that is an amorphous silicon filmhere is formed on the silicon oxide film 55 and in contact thereto.

[0135] Further, because here it is possible to form the silicon oxidefilm 55 and the semiconductor film 56 with the same film depositionmethod, both films may be formed in succession in the same chamber.After the formation of the silicon oxide film 55, it becomes possible toprevent contamination of the surface by not exposing the substrate tothe open atmosphere for a time during the conveying of the substrate. Asa result, characteristic irregularities of the manufactured TFTs can bereduced.

[0136] Thereafter, a known crystallization technique is carried out tothereby form a crystalline semiconductor film on the substrate with thelaminate layer of the first insulating film 52, the silicon nitrideoxide film 53, the second insulating film 54, the silicon oxide film 55and the amorphous semiconductor film formed thereon.

[0137] Known techniques may be used for the remaining processes to formthe TFT.

[0138] [Embodiment 6]

[0139] In this embodiment, a case where one embodiment of the presentinvention is applied to an active matrix liquid crystal display devicewill be described with reference to FIGS. 6 to 12.

[0140]FIG. 6A is a cross sectional view, and reference numeral 101 showsan insulating substrate, for example, a substrate of 1737 glass made byCorning Inc. is used. On the glass substrate, a base film 102 comprisinga silicon nitride oxide film in which a composition of nitrogen oroxygen undergoes a continuous change and an amorphous semiconductor film103 are formed as a lamination film. As a method of forming thelamination film, any one of Embodiments 1 to 5 described above may beused. In Embodiment 6, the method shown in Embodiment 1 is used to forma base film having a thickness of 200 nm and an amorphous silicon filmhaving a thickness of 50 nm.

[0141] Next, the amorphous silicon film is preferably heated at 400 to550° C. for several hours to carry out a dehydrogenating processdepending on the amount of hydrogen contained in the amorphous siliconfilm, so that the hydrogen content is made 5 atom % or less, and a stepof crystallization is carried out.

[0142] As a step of crystallizing the amorphous silicon film, awell-known laser crystallization method or a thermal crystallizationmethod may be used. In this embodiment, a pulse oscillation type KrFexcimer laser light was linearly condensed and was irradiated to theamorphous silicon film to form a crystalline silicon film.

[0143] The thus formed crystalline silicon film was patterned by using afirst photomask to form island-like semiconductor layers 103, 104 and105.

[0144] Note that the crystalline silicon film is formed from theamorphous silicon film as the island-like semiconductor layer in thisembodiment, however a microcrystal silicon film may be used, or acrystalline silicon film may be directly formed.

[0145] Next, a gate insulating film 106 containing silicon oxide orsilicon nitride as its main component was formed to cover theisland-like semiconductor layers 103, 104, and 105. As the gateinsulating film 106, a silicon nitride oxide film having a thickness of10 to 200 nm, preferably 50 to 150 nm may be formed by a plasma CVDmethod using N₂O and SiH₄ as a source material. Here, the film wasformed to a thickness of 100 nm. (FIG. 6A)

[0146] Then resist masks 107, 108, 109, 110 and 111 covering channelforming regions of the semiconductor layer 103 and the semiconductorlayers 104 and 105 were formed through a second photomask. At this time,a resist mask 109 may be formed also in a region where the wiring isformed.

[0147] Then, a step of adding an impurity element which gives the n-typeto form a second impurity region was carried out. Here, phosphorus wasused and an ion doping method using phosphine (PH₃) was carried out. Inthis step, for the purpose of adding phosphorus through the gateinsulating film 106 to a semiconductor layer thereunder, an accelerationvoltage was set as high as 65 KeV. It is preferable that a concentrationof phosphorus added in the semiconductor layer is made a value withinthe range of 1×10¹⁶ to 1×10¹⁹ atoms/cm³, and here, it was made 1×10¹⁸atoms/cm³. Then, regions 112, 113, 114, 115, and 116 where phosphorus(P) was added in the semiconductor layer were formed. Here, one part ofthe regions where phosphorus was added are made second impurity regionsfunctioning as LDD regions (FIG. 6B).

[0148] Thereafter, the resist masks were removed and a first conductivelayer 117 was formed on the whole surface. As the first conductive layer117, a conductive material containing an element selected from Ta, Ti,Mo, and W is used. It is appropriate that the first conductive layer 117is formed to a thickness of 100 to 1,000 nm, preferably 150 to 400 nm.In this embodiment, Ta is formed by sputtering. (FIG. 6C)

[0149] Next, resist masks 118, 119, 120, 121, 122, and 123 were formedwith a third photomask. The fourth photomask is for forming a gateelectrode of a p-channel TFT, gate wirings of a CMOS circuit and a pixelportion, gate bus lines. Since a gate electrode of an n-channel TFT wasformed in a later step, the resist masks 119 and 123 were formed so thatthe first conductive layer 117 remained on a whole surface of thesemiconductor layer 104.

[0150] Unnecessary portions of the first conductive layer were removedby a dry etching method. Etching of Ta is performed by mixed gas of CF₄and O₂. Then, a gate electrode 124, gate wirings 126 and 128, and a gatebus line 127 were formed.

[0151] A doping step of a third impurity element giving the p-type to apart of the semiconductor layer 103 where the p-channel TFT was to beformed was carried out while the resist masks 118, 119, 120, 121, 122,and 123 were made to remain as they were. In this embodiment, boron wasused as the impurity element and was added by an ion doping method usingdiborane (B₂H₆). Also in this case, an acceleration voltage was made 80keV, and boron was added at a concentration of 2×10²⁰ atoms/cm³. Asshown in FIG. 7A, third impurity regions 130 and 131 where boron wasadded at a high concentration were formed.

[0152] After the resist masks provided in FIG. 7A were removed, resistmasks 132, 133, 134, 135, 136, 137, and 138 were newly formed with afourth photomask. The fourth photomask is for forming gate electrodes ofn-channel TFTs, and gate electrodes 139, 140, 141 and capacitanceelectrode 142 were formed by a dry etching method. At this time, thegate electrodes 139, 140, and 141 were formed to overlap with part ofthe second impurity regions 112, 113, 114, 115 and 116. (FIG. 7B)

[0153] After the resist masks were removed, new resist masks 143, 144,145, 146, 147, 148, and 149 were formed. The resist masks 144, 147, and148 were formed to cover the gate electrodes 139, 140, and 141 of then-channel TFTs and part of the second impurity regions. The resist masks144, 147, and 148 determine the offset amounts of LDD regions.

[0154] Then, a doping step of an impurity element giving the n-type wascarried out to form a first impurity region. First impurity regions 151and 152 which became source regions and first impurity regions 150, 153,and 154 which became drain regions were formed. Here, the step wascarried out by an ion doping method using phosphine (PH₃). Also in thisstep, for the purpose of adding phosphorus through the gate insulatingfilm 106 to the semiconductor layer under the film, an accelerationvoltage was set as high as 80 KeV. A concentration of phosphorus in theregions is high as compared with the prior doping step of the firstimpurity element giving the n-type, and it is preferable that theconcentration is made 1×10¹⁹ to 1×10²¹ atoms/cm³, and here, it was made1×10²⁰ atoms/cm³. (FIG. 7C)

[0155] After the steps up to FIG. 7C were completed, a step of formingfirst interlayer insulating films 155 and 156 was carried out. First, asilicon nitride film 155 was formed to be a lower layer to a thicknessof 50 nm. The silicon nitride film 155 was formed by a plasma CVD methodunder the condition that SiH₄ of 5 SCCM, NH₃ of 40 SCCM, and N₂ of 100SCCM were introduced, the pressure was made 0.7 Torr, and a highfrequency power of 300 W was applied. Subsequently, as the firstinterlayer insulating film 156 to be an upper layer, a silicon oxidefilm having a thickness of 950 nm was formed under the condition thatTEOS of 500 SCCM and O₂ of 50 SCCM were introduced, the pressure wasmade 1 Torr, and a high frequency power of 200 W was applied. (FIG. 8)

[0156] Then, a step of heat treatment was carried out. It was necessaryto carry out the step of heat treatment to activate the impurity elementadded at each concentration to give the - type or p-type. This step maybe carried out by a thermal annealing method using an electric heatingfurnace, the foregoing laser annealing method using an excimer laser, ora rapid thermal annealing method (RTA method) using a halogen lamp.Here, the step of activation was carried out by the thermal annealingmethod. The heat treatment was carried out in a nitrogen atmosphere at300 to 700° C., preferably 350 to 550° C., here, 450° C. for 2 hours.

[0157] Thereafter, the first interlayer insulating films 155 and 156were patterned to form contact holes reaching a source region and adrain region of each TFT. Then, source electrodes 157, 158, and 159 anddrain electrodes 160 and 161 were formed. Although not shown, in thisembodiment, the respective electrodes were formed as a three-layerelectrode in which a Ti film having a thickness of 100 nm, an Al filmcontaining Ti and having a thickness of 300 nm, and a Ti film having athickness of 150 nm were continuously formed by a sputtering method.

[0158] Through the foregoing steps, a channel forming region 165, firstimpurity regions 168 and 169, and second impurity regions 166 and 167were formed in the n-channel TFT of the CMOS circuit. Here, in thesecond impurity regions, regions (GOLD regions) 166 a and 167 aoverlapping with the gate electrode and regions (LDD regions) 166 b and167 b not overlapping with the gate electrode were formed, respectively.The first impurity region 168 became a source region and the firstimpurity region 169 became a drain region.

[0159] In the p-channel TFT, a channel forming region 162, and thirdimpurity regions 163 and 164 were formed. Then, the third impurityregion 163 became a source region and the third impurity region 164became a drain region.

[0160] Further, the n-channel TFT of the pixel portion has a multi gatestructure, and channel forming regions 170 and 171, first impurityregions 176 and 177, and second impurity regions 172, 173, 174 and 175were formed. Here, in the second impurity regions, regions 172 a, 173 a,174 a and 175 a overlapping with the gate electrode, and regions 172 b,173 b, 174 b and 175 b not overlapping with the gate electrode wereformed.

[0161] In this way, as shown in FIG. 8, an active matrix substrate inwhich the CMOS circuit and the pixel portion were formed over thesubstrate 101 was fabricated. At the same time, a storage capacitancewas formed with a low concentration impurity region 178 to which animpurity element giving n-type is added at a same concentration as thatof the second impurity region, a gate insulating film 106, and acapacitance electrode 142 at the drain side of the n-channel TFT of thepixel portion.

[0162] Then, a description will be made on a process of fabricating anactive matrix type liquid crystal display device from an active matrixsubstrate.

[0163] A passivation film 179 was formed to the active matrix substratein the state of FIG. 8. The passivation film 179 was made of a siliconnitride film having a thickness of 50 nm. Further, a second interlayerinsulating film 180 made of organic resin was formed to a thickness ofabout 1,000 nm. As the organic resin film, polyimide, acryl,polyimidoamide, etc. may be used. As advantages obtained by using theorganic resin film, it is possible to enumerate such points that a filmformation method is simple, parasitic capacitance can be reduced sinceits relative dielectric constant is low, and flatness is superior. Anorganic resin film other than the above may be used. Here, polyimide ofsuch a type that thermal polymerization was made after application tothe substrate was used, and was fired at 300° C. to form the film. (FIG.9A)

[0164] Further, a third interlayer insulating film 181 was formed. Thethird interlayer insulating film 181 was formed by using an organicresin film of polyimide or the like. Then, a contact hole reaching thedrain electrode 161 was formed by selectively removing the thirdinterlayer insulating film 181, the second interlayer insulating film180, and the passivation film 179, and a pixel electrode 182 was formed.With respect to the pixel electrode 182, it is appropriate that atransparent conductive film is used in the case where a transmissiontype liquid crystal display device is formed, and a metal film is usedin the case where a reflection type liquid crystal display device isformed. Here, for the purpose of making the transmission type liquidcrystal display device, an indium-tin oxide (ITO) film having athickness of 100 nm was formed by a sputtering method and patterning isperformed, so that the pixel electrode 182 was formed. (FIG. 9B)

[0165] Next, as shown in FIG. 10, an orientation film 183 was formed onthe third interlayer insulating film 181 and the pixel electrode 182. Ingeneral, a polyimide resin is often used for an orientation film of aliquid crystal display device. A transparent conductive film 185 and anorientation film 186 were formed on an opposite side substrate 184. Theorientation film was subjected to a rubbing process after formation sothat liquid crystal molecules were made to be oriented in parallel andwith a certain pretilt angle.

[0166] After the foregoing steps, the active matrix substrate on whichthe pixel portion and the CMOS circuit were formed and the oppositesubstrate were bonded to each other by a well-known cell assembling stepthrough a sealing material, a spacer (both are not shown), and the like.Thereafter, a liquid crystal material 187 was injected between both ofthe substrates, and complete sealing was made by a sealing agent (notshown). Thus, the active matrix type liquid crystal display device shownin FIG. 10 was completed.

[0167] Next, a structure of an active matrix type liquid crystal displaydevice of this embodiment will be described with reference to FIGS. 11and 12. FIG. 11 is a perspective view of an active matrix substrate ofthis embodiment. The active matrix substrate is constructed by a pixelportion 601, a scanning (gate) line driver circuit 602, a signal(source) line driver circuit 603, and a logic circuit 604 formed on aglass substrate 101. A pixel TFT 600 of a pixel portion is an n-channelTFT, and the driver circuits provided at the periphery comprise a CMOScircuit as a base. The scanning (gate) line driver circuit 602 and thesignal (source) line driver circuit 603 are connected to the pixelportion 601 through a gate wiring 605 and a source wiring 606,respectively. The pixel portion 601 is formed with a pixel TFT 600, apixel electrode 607, and a storage capacitance 608.

[0168] In this embodiment, although the pixel TFT 600 has a double gatestructure, a single gate structure may be adopted, or a multi gatestructure of a triple gate may be adopted. The structure of the activematrix substrate is not limited to the structure of this embodiment.Since the structure of the present invention is characterized in thestructure of a base film, other structures may be suitably determined byan operator.

[0169]FIG. 12 is a top view of the pixel portion 601 and is a top viewof almost one pixel. The pixel portion is provided with an n-channelTFT. A gate electrode 1202 intersects through a not-shown gateinsulating film with a semiconductor layer 1201 thereunder. Although notshown, a source region, a drain region, and a first impurity region areformed in the semiconductor layer. At a drain side of the pixel TFT, astorage capacitance 1207 comprises the semiconductor layer, the gateinsulating film, and an electrode made of the same material as the gateelectrode. A sectional structure along line A-A′ and line B-B′ shown inFIG. 12 corresponds to the sectional view of the pixel portion shown inFIG. 10.

[0170] [Embodiment 7]

[0171] In this embodiment, a description will be made on an examplewhere a crystalline semiconductor film used as the semiconductor layerin the embodiment 6 is formed by a thermal crystallization method usinga catalytic element. In the case where the catalytic element is used, itis desirable to use a technique disclosed in Japanese Patent ApplicationLaid-open No. Hei. 7-130652 or Hei. 8-78329.

[0172] Here, an example of a case where the technique disclosed inJapanese Patent Application Laid-open No. Hei. 7-130652 is applied tothe present invention will be described in FIG. 13. First, a base film1302 comprising a silicon nitride oxide film in which a composition ofnitrogen or oxygen undergoes a continuous change was formed on asubstrate 1301 and an amorphous silicon film 1303 was formed thereon. Asa method of forming the lamination film, any one of Embodiments 1 to 5described above may be used. In Embodiment 7, the method shown inEmbodiment 1 is used to form a base film having a thickness of 250 nmand an amorphous silicon film having a thickness of 50 nm.

[0173] Thereafter, a nickel acetate salt solution containing nickel of10 ppm in terms of weight was applied, thereby forming a nickelcontaining layer 1304. (FIG. 13A)

[0174] Next, after a dehydrogenating step at 500° C. for 1 hour wascarried out, a heat treatment at 500 to 650° C. for 4 to 12 hours, forexample, at 550° C. for 8 hours was carried out, so that a crystallinesilicon film 1305 was formed. The crystalline silicon film 1305 obtainedin this way had extremely superior crystallinity. (FIG. 13B)

[0175] The technique disclosed in Japanese Patent Application Laid-openNo. Hei. 8-78329 is such that selective crystallization of an amorphoussemiconductor film is made possible by selectively adding a catalyticelement. A case where the technique is applied to the present inventionwill be described with reference to FIG. 14.

[0176] First, a base film 1402 comprising a silicon nitride oxide filmin which a composition of nitrogen or oxygen undergoes a continuouschange was formed on a glass substrate 1401 and an amorphous siliconfilm 1403 and a silicon oxide film 1404 were continuously formedthereon. At this time, the thickness of the silicon oxide film 1404 wasmade 150 nm. As a method of forming the base film 1402, any one ofEmbodiments 1 to 5 described above may be used. In Embodiment 7, themethod shown in Embodiment 2 is used to form a base film.

[0177] Next, the silicon oxide film 1404 was patterned to selectivelyform opening portions 1405. Thereafter, a nickel acetate salt solutioncontaining nickel of 10 ppm in terms of weight was applied. By this, anickel containing layer 1406 was formed, and the nickel containing layer1406 was brought into contact with the amorphous silicon film 1902 atonly the bottoms of the opening portions 1405 (FIG. 14A).

[0178] Next, a heat treatment at 500 to 650° C. for 4 to 24 hours, forexample, at 570° C. for 14 hours was carried out, so that a crystallinesilicon film 1407 was formed. In this crystallizing process, a portionof an amorphous silicon film with which nickel is in contact is firstcrystallized, and crystal growth progresses in the lateral directiontherefrom. The thus formed crystalline silicon film 1407 comprises acollective of rod-like or needle-like crystals, and each crystalmacroscopically grows with certain directionality. Thus, there is anadvantage that crystallinity is uniform (FIG. 14B).

[0179] In the foregoing two techniques, instead of nickel (Ni), acatalytic element such as germanium (Ge), iron (Fe), palladium (Pd), tin(Sn), lead (Pb), cobalt (Co), platinum (Pt), copper (Cu), or gold (Au)may be used.

[0180] If a crystalline semiconductor film (including a crystallinesilicon film, a crystalline silicon germanium film, etc.) is formed byusing the technique as described above, and patterning is carried out, asemiconductor layer of a crystalline TFT can be formed. Althoughsuperior characteristics can be obtained in the TFT fabricated from thecrystalline semiconductor film by using the technique of thisembodiment, high reliability has been required because of that. However,when the TFT structure of the present invention is adopted, it becomespossible to fabricate a TFT which utilizes the technique of thisembodiment to the utmost.

[0181] [Embodiment 8]

[0182] In this embodiment, a description will be made on an example inwhich as a method of forming a semiconductor layer used in theembodiment 6, after a crystalline semiconductor film is formed using anamorphous semiconductor film as an initial film and using a catalyticelement, a step of removing the catalytic element from the crystallinesemiconductor film is carried out. As a method thereof, this embodimentuses a technique disclosed in Japanese Patent Application Laid-open No.Hei 10-135468, or Hei 10-135469.

[0183] The technique disclosed in the publications is such that acatalytic element used for crystallization of an amorphous semiconductorfilm is removed after crystallization by using a gettering function ofphosphorus. By using the technique, it is possible to reduce aconcentration of a catalytic element in a crystalline semiconductor filmto 1×10¹⁷ atoms/cm³ or less, preferably 1×10¹⁶ atoms/cm³ or less.

[0184] A structure of this embodiment will be described with referenceto FIG. 15. Here, an alkali-free glass substrate typified by a substrateof 1737 glass made by Corning Inc. was used. FIG. 15A shows a state inwhich a base film 1502 and a crystalline silicon film 1503 were formedby using the technique disclosed in the embodiment 7. As a method offorming the base film 1502, any one of Embodiments 1 to 5 describedabove may be used. Then, a silicon oxide film 1504 for masking wasformed to a thickness of 150 nm on the surface of the crystallinesilicon film 1503, and opening portions were provided by patterning, sothat regions where the crystalline silicon film was exposed wereprovided. Then, a step of adding phosphorus was carried out so that aregion 1505 added with phosphorus was provided in the crystallinesilicon film.

[0185] In this state, when a heat treatment at 550 to 800° C. for 5 to24 hours, for example, at 600° C. for 12 hours was carried out in anitrogen atmosphere, the region 1505 where phosphorus was added in thecrystalline silicon film functioned as a gettering site, so that it waspossible to segregate the catalytic element remaining in the crystallinesilicon film 1503 into the region 1505 added with phosphorus.

[0186] By removing the silicon oxide film 1504 for masking and theregion 1505 added with phosphorus with etching, it was possible toobtain a crystalline silicon film in which the concentration of thecatalytic element used in the step of crystallization was reduced to1×10¹⁷ atoms/cm³ or less. It was possible to use this crystallinesilicon film without any change as the semiconductor layer of the TFT ofthe present invention described in the embodiment 6.

[0187] [Embodiment 9]

[0188] CMOS circuits and pixel portions formed by implementing thepresent invention can be used in various electro-optical devices(typically, an active matrix liquid crystal display device and thelike). Namely, the present invention can be implemented in allelectronic apparatus in which these electro-optical devices are builtinto a display portion.

[0189] The following can be given as such electronic apparatus: a videocamera, a digital camera, a projector (rear type or front type), ahead-mounted display (a goggle type display), a car navigation system, acar stereo, a personal computer, and a portable information terminal(such as a mobile computer, a portable telephone or an electronic book).Examples of these are shown in FIGS. 16, 17 and 18.

[0190]FIG. 16A is a personal computer, and it includes a main body 2001,an image input portion 2002, a display portion 2003, and a keyboard2004, etc. The present invention can be applied to the image inputportion 2002, the display portion 2003 or other signal controllingcircuits.

[0191]FIG. 16B is a video camera, and it includes a main body 2101, adisplay portion 2102, an audio input portion 2103, operation switches2104, a battery 2105, and an image receiving portion 2106, etc. Thepresent invention can be applied to the display portion 2102 or othersignal controlling circuits.

[0192]FIG. 16C is a mobile computer, and it includes a main body 2201, acamera portion 2202, an image receiving portion 2203, operation switches2204, and a display portion 2205. The present invention can be appliedto the display portion 2205 or other signal controlling circuits.

[0193]FIG. 16D is a goggle type display, and it includes a main body2301, a display portion 2302, an arm portion 2303, etc. The presentinvention can be applied to the display portion 2302 or other signalcontrolling circuits.

[0194]FIG. 16E is a player that uses a recording medium on which aprogram is recorded (hereafter referred to as a recording medium), andthe player includes a main body 2401, a display portion 2402, a speakerportion 2403, a recording medium 2404, and operation switches 2405, etc.Note that this player uses a recording medium such as a DVD (digitalversatile disk) or a CD, and the appreciation of music, the appreciationof film, game playing and the Internet can be performed. The presentinvention can be applied to the display portion 2402 or other signalcontrolling circuits.

[0195]FIG. 16F is a digital camera, and it includes a main body 2501, adisplay portion 2502, an eyepiece portion 2503, operation switches 2504,and an image receiving portion (not shown in the figure), etc. Thepresent invention can be applied to the display portion 2502 or othersignal controlling circuits.

[0196]FIG. 17A is a front projector, and it includes a projection system2601, a screen 2602, etc. The present invention can be applied to aliquid crystal display device 2808 which constitutes a part of theprojection system 2601, or other signal controlling circuits.

[0197]FIG. 17B is a rear projector, and it includes a main body 2701, aprojection system 2702, a mirror 2703, a screen 2704, etc. The presentinvention can be applied to a liquid crystal display device 2808 whichconstitutes a part of the projection system 2702 or other signalcontrolling circuits.

[0198] Note that FIG. 17C is a diagram showing an example of thestructure of projection systems 2601 and 2702 of FIGS. 17A and 17B. Theprojection systems 2601 and 2702 comprise an optical light source system2801, mirrors 2802 and 2804 to 2806, a dichroic mirror 2803, a prism2807, a liquid crystal display device 2808, phase differentiating plate2809 and a projection optical system 2810. The projection optical system2810 comprises an optical system including a projection lens. Thepresent Embodiment showed a three plate type, but it is not limited tothis structure, and it may be for instance a single plate type. Further,the operator may appropriately dispose an optical system such as anoptical lens, a film having light polarizing function, a film foradjusting phase difference and an IR film, in the optical path shown byan arrow in the FIG. 17C.

[0199]FIG. 17D is a diagram showing an example of the structure of theoptical light source system 2801 of FIG. 17C. In the present Embodimentthe optical light source system 2801 comprises a reflector 2811, a lightsource 2812, lens arrays 2813 and 2814, light polarizing conversionelement 2815 and a condenser lens 2816. Note that the optical lightsource system shown in FIG. 17D is merely an example and is notspecifically limited. For example, the operator may appropriatelydispose an optical system such as an optical lens, a film having lightpolarizing function, a film for adjusting phase difference and an IRfilm, etc., in the optical light source system.

[0200] Provided however, the projectors shown in FIG. 17 show a case ofusing a transmission type electro-optical device and an applicationexample of a reflection type electro-optical device is not shown in thefigures.

[0201]FIG. 18A is a portable telephone, and it includes a main body2901, an audio output portion 2902, an audio input portion 2903, adisplay portion 2904, operation switches 2905, and an antenna 2906, etc.The present invention can be applied to the audio output portion 2902,the audio input portion 2903, the display portion 2904 or other signalcontrolling circuits.

[0202]FIG. 18B is a portable book (electronic book), and it includes amain body 3001, display portions 3002 and 3003, a recording medium 3004,operation switches 3005, and an antenna 3006, etc. The present inventioncan be applied to the display portions 3002 and 3003 or other signalcontrolling circuits.

[0203]FIG. 18C is a display, and it includes a main body 3101, a supportstand 3102, and a display portion 3103, etc. The present invention canbe applied to the display portion 3103. The display of the presentinvention is advantageous for a large size screen in particular, and isadvantageous for a display equal to or greater than 10 inches(especially equal to or greater than 30 inches) in the opposite angle.

[0204] The applicable range of the present invention is thus extremelywide, and it is possible to apply the present invention to electronicapparatus in all fields. Further, the electronic apparatus of thisembodiment can be realized by using a constitution of any combination ofembodiments 1 to 8.

[0205] Therefore, from TFT characteristics so far, it is possible tomake remarkable progress in the electric characteristic of the thusobtained TFT using the semiconductor film, which is formed on the basefilm containing the silicon nitride oxide film of the present invention,as an active layer.

What is claimed is:
 1. A semiconductor device having a thin filmtransistor, said semiconductor device comprising: an insulating filmformed over a substrate; and a semiconductor film formed over saidinsulting film, wherein said insulating film comprises a silicon nitrideoxide film in which a concentration ratio of nitrogen to silicon thereinundergoes a continuous change within a range of 0.3 to 1.6.
 2. Asemiconductor device having a thin film transistor, said semiconductordevice comprising: an insulating film formed over a substrate; and asemiconductor film formed over said insulating film, wherein saidinsulating film comprises a silicon nitride oxide film in which aconcentration ratio of oxygen to silicon therein undergoes a continuouschange within a range of 0.1 to 1.7.
 3. A semiconductor device having athin film transistor, said semiconductor device comprising: aninsulating film formed over a substrate; and a semiconductor film formedover said insulating film, wherein said insulating film comprises asilicon nitride oxide film in which a concentration ratio of nitrogen tosilicon therein undergoes a continuous change within a range of 0.3 to1.6, and wherein a concentration ratio of oxygen to silicon thereinundergoes a continuous change within a range of between 0.1 to 1.7.
 4. Asemiconductor device having a thin film transistor, said semiconductordevice comprising: a first insulating film comprising a silicon nitrideoxide film formed over a substrate; a second insulating film formed incontact with said first insulating film; and a semiconductor film formedover said first and second insulating films, wherein a concentrationratio of nitrogen to silicon in said first insulating film undergoes acontinuous change within a range of 0.3 to 1.6.
 5. A semiconductordevice having a thin film transistor, said semiconductor devicecomprising: a first insulating film comprising a silicon nitride oxidefilm formed over a substrate; a second insulating film formed in contactwith said first insulating film; and a semiconductor film formed oversaid first and second insulating films, wherein a concentration ratio ofoxygen to silicon in said silicon nitride oxide film undergoes acontinuous change within a range of 0.1 to 1.7.
 6. A semiconductordevice having a thin film transistor, said semiconductor devicecomprising: a silicon nitride oxide film formed over a substrate; asilicon oxide film formed in contact with said silicon nitride oxidefilm; and a semiconductor film formed over said silicon oxide film,wherein a concentration ratio of nitrogen to silicon in said siliconnitride oxide film undergoes a continuous change within a range of 0.3to 1.6.
 7. A semiconductor device having a thin film transistor, saidsemiconductor device comprising: a silicon nitride oxide film formedover a substrate; a silicon oxide film formed in contact with saidsilicon nitride oxide film; and a semiconductor film formed over saidsilicon oxide film, wherein a concentration ratio of oxygen to siliconin said silicon nitride oxide film undergoes a continuous change withina range of 0.1 to 1.7.
 8. A semiconductor device according to any one ofclaims 1, 3, 4 and 6, wherein said concentration ratio of nitrogen tosilicon in said silicon nitride oxide film continuously decreases towardan interface of said semiconductor film side.
 9. A semiconductor deviceaccording to any one of claims 2, 3, 5 and 7, wherein said concentrationratio of oxygen to silicon in said silicon nitride oxide filmcontinuously increases toward an interface of said semiconductor filmside.
 10. A semiconductor device according to any one of claims 1 to 7 ,wherein said semiconductor device is selected from the group consistingof a video camera, a digital camera, a projector, a goggle type display,a car navigation unit, a car stereo, a personal computer, and a portableinformation terminal.
 11. A method of manufacturing a semiconductordevice, comprising the steps of: forming a silicon nitride oxide filmformed over a substrate; and forming a semiconductor film formed oversaid silicon nitride oxide film, wherein a concentration ratio ofnitrogen to silicon in said silicon nitride oxide film undergoes acontinuous change within a range of 0.3 to 1.6 by continuously alteringa gas flow rate.
 12. A method of manufacturing a semiconductor device,comprising the steps of: forming a silicon nitride oxide film formedover a substrate; and forming a semiconductor film formed over saidsilicon nitride oxide film, wherein a concentration ratio of oxygen tosilicon in said silicon nitride oxide film undergoes a continuous changewithin a range of 0.1 to 1.7 by continuously altering a gas flow rate.13. A method of manufacturing a semiconductor device, comprising thesteps of: forming a silicon nitride oxide film formed over a substrate;and forming a semiconductor film formed over said said silicon nitrideoxide film, wherein a concentration ratio of nitrogen to silicon in saidsilicon nitride oxide film undergoes a continuous change within a rangeof 0.3 to 1.6 by continuously altering a gas ratio.
 14. A method ofmanufacturing a semiconductor device, comprising the steps of: forming asilicon nitride oxide film formed over a substrate; and forming asemiconductor film formed over said silicon nitride oxide film, whereina concentration ratio of oxygen to silicon in said silicon nitride filmundergoes a continuous change within a range of 0.1 to 1.7 bycontinuously altering a gas ratio.
 15. A method of manufacturing asemiconductor device, comprising the steps of: forming a silicon nitrideoxide film formed over a substrate; and forming a semiconductor filmformed over said silicon nitride oxide film, wherein a concentrationratio of nitrogen to silicon in silicon nitride oxide film undergoes acontinuous change within a range of 0.3 to 1.6 by continuously alteringan RF output.
 16. A method of manufacturing a semiconductor device,comprising the steps of: forming a silicon nitride oxide film formedover a substrate; and forming a semiconductor film formed over saidsilicon nitride oxide film, wherein a concentration ratio of oxygen tosilicon in said silicon nitride oxide film undergoes a continuous changewithin a range of 0.1 to 1.7 by continuously altering an RF output. 17.A method of manufacturing a semiconductor device, comprising the stepsof: forming a silicon nitride oxide film formed over a substrate; andforming a semiconductor film formed over said silicon nitride oxidefilm, wherein a concentration ratio of nitrogen to silicon in saidsilicon nitride oxide film undergoes a continuous change within a rangeof 0.3 to 1.6, and wherein said silicon nitride oxide film and saidsemiconductor film are formed consecutively in a same chamber.
 18. Amethod of manufacturing a semiconductor device, comprising the steps of:forming a silicon nitride oxide film formed over a substrate; andforming a semiconductor film formed over said silicon nitride oxidefilm, wherein a concentration ratio of oxygen to silicon in said siliconnitride oxide film undergoes a continuous change within a range of 0.1to 1.7, and wherein said silicon nitride oxide film and saidsemiconductor film are formed consecutively in a same chamber.
 19. Amethod of manufacturing a semiconductor device, comprising the steps of:forming an insulating film formed over a substrate; forming a siliconnitride oxide film formed over said insulating film; and forming asemiconductor film formed over said silicon nitride oxide film, whereina concentration ratio of nitrogen to silicon in said silicon nitrideoxide film undergoes a continuous change within a range of 0.3 to 1.6,and wherein said silicon nitride oxide film and said semiconductor filmare formed consecutively in a same chamber.
 20. A method ofmanufacturing a semiconductor device, comprising the steps of: formingan insulating film formed over a substrate; forming a silicon nitrideoxide film formed over said insulating film; and forming a semiconductorfilm formed over said silicon nitride oxide film, wherein aconcentration ratio of oxygen to silicon in said silicon nitride oxidefilm undergoes a continuous change within a range of 0.1 to 1.7, andwherein said silicon nitride oxide film and said semiconductor film areformed consecutively in a same chamber.
 21. A method of manufacturing asemiconductor device, comprising the steps of; forming a silicon nitrideoxide film formed over a substrate; forming an insulating film formedover said silicon nitride oxide film; and forming a semiconductor filmformed over said insulating film, wherein a concentration ratio ofnitrogen to silicon in said silicon nitride oxide film undergoes acontinuous change within a range of 0.3 to 1.6, and wherein said siliconnitride oxide film, said insulating film and said semiconductor film areformed consecutively in a same chamber.
 22. A method of manufacturing asemiconductor device, comprising the steps of: forming a silicon nitrideoxide film formed over a substrate; forming an insulating film formedover said silicon nitride oxide film; and forming a semiconductor filmformed in contact with said insulating film, wherein a concentrationratio of oxygen to silicon in said silicon nitride oxide film undergoesa continuous change within a range of 0.1 to 1.7, and wherein saidsilicon nitride oxide film, said insulating film and said semiconductorfilm are formed consecutively in a same chamber.
 23. A method ofmanufacturing a semiconductor device, comprising the steps of: forming afirst insulating film formed over a substrate; forming a silicon nitrideoxide film formed over said first insulating film; and forming a secondinsulating film formed over said silicon nitride oxide film, wherein aconcentration ratio of nitrogen to silicon in said silicon nitride oxidefilm undergoes a continuous change within a range of 0.3 to 1.6, andwherein said silicon nitride oxide film and said second insulating filmare formed consecutively in a same chamber.
 24. A method ofmanufacturing a semiconductor device, comprising the steps of: forming afirst insulating film formed over a substrate; forming a silicon nitrideoxide film formed over said first insulating film; forming a secondinsulating film formed over said silicon nitride oxide film; and forminga semiconductor film formed over said second insulating film, wherein aconcentration ratio of oxygen to silicon in said silicon nitride oxidefilm undergoes a continuous change within a range of 0.1 to 1.7, andwherein said silicon nitride oxide film, said second insulating film andsaid semiconductor film are formed consecutively in a same chamber. 25.A method of manufacturing a semiconductor device according to any one ofclaims 11, 13, 15, 17, 19, 21 and 23 wherein said concentration ratio ofnitrogen to silicon in said silicon nitride oxide film continuouslydecreases toward an interface of said semiconductor film side.
 26. Amethod of manufacturing a semiconductor device according to any one ofclaims 12, 14, 16, 18, 20, 22 and 24, wherein said concentration ratioof oxygen to silicon in said silicon nitride oxide film continuouslyincreases toward an interface of said semiconductor film side.